The instant invention relates to a one-part room temperature vulcanizing (RTV) silicone rubber compositions which can be extruded at a high application rate and also exhibits a resistance to flow vertically when applied to a vertical surface. More particularly this invention relates to ketoxime RTV rubber compositions capable of high rates of extrusion while maintaining good resistance to vertical flow.
RTV rubber compositions are known in the art. Such compositions are known for their ability to resist change at elevated temperatures and exposure to adverse conditions over extended periods of time. In general, materials are needed which have outstanding properties such as good tensile strength and the ability to retain those outstanding properties when challenged by exposure to chemical agents known to reduce or diminish performance.
Successful efforts have been made to produce RTV elastomer, compositions having increased strength and adhesion. For example ketoxime sealants as set forth in U.S. patent application Ser. No. 07/857,202, filed Mar. 25, 1992, pending, entitled "One Part Room Temperature Vulcanizing Compositions with Improved Oil Resistance and Adhesion, assigned to General Electric Company, incorporated herein by reference, exhibit such desirable properties. When such ketoxime sealants are compounded continuously, the cross linker, adhesion promoter (when used), and catalyst are commonly added to an extruder as a single solution in a one step catalyzation. The resulting composition has good physical properties but is difficult to apply at high rates.
Successful efforts have been made to produce RTV elastomer compositions having increased strength and adhesion. For example, ketoxime sealants as set forth in U.S. patent application Ser. No. 07/981,571, filed Nov. 25, 1992, now abandoned entitled "One Part Room Temperature Vulcanizing Composition Having a High Rate of Extrusion," assigned to General Electric Company, incorporated herein by reference exhibit such desirable properties. When such ketoxime sealants are compounded continuously the catalyzation is divided wherein the cross linking agent and an optional adhesion promoter are added to an extruder followed by the addition of the tin containing catalyst further down the extruder. This two step catalyzation results in sealants that possess both good physical properties and the ability to be applied at a high rate of application, however the ability of the sealant composition to resist gravity induced flow when applied to a vertical surface could be improved. It is therefor very desirable to provide RTV compositions having not only good tensile strength, fast cure rates, and good room temperature adhesion but which may also be applied at a high rate of application and when applied to a vertical surface exhibit a low rate of gravity induced flow from the point of application.